The present invention relates generally to clutches such as those used in conjunction with automotive power steering systems and more particularly to a new and improved clutch system and torque limitation system, both especially for useful in conjunction with automotive power steering systems. The new and improved clutch system includes a passively actuated system that permits torque transmission from one direction only. The torque limitation system includes a feature for allowing slip, for example, at or above a preset torque level.
The advent of automotive electric power assisted steering (EPAS) systems will greatly enhance the ease of steering and overall drivability of modern automobiles. This is especially true for individuals, such as the elderly and the disabled, who may not possess the requisite physical strength to turn an unassisted (i.e., un-powered) automobile steering wheel in a reasonably safe and effective manner.
However, there are several problems with electrical power steering systems. For example, in the event of a failure of the automobile""s electrical system or the electrical power assist motor; the torque necessary to turn the steering wheel would be relatively unsafe due to the high-speed reduction ratio in the system. Such difficulty in turning the steering wheel could potentially result in an increased frequency of accidents.
Additionally, xe2x80x9ckickbackxe2x80x9d from impact with road hazards, such as curbs, bumps, potholes, and so forth, can potentially damage the power steering system""s speed reduction system.
Therefore, there exists a need for a new and improved power steering system wherein torque is transmitted from one direction (e.g., input side) only, and allows the system to be decoupled completely from the power steering motor when torque is forced in from the output side. Additionally, the new and improved power steering system should include a torque limiting system that permits slip when overall torque exceeds a preset and/or predetermined limit.
In accordance with the general teachings of the present invention, a clutch system is provided wherein torque transmission is permitted out in one direction only (i.e., output side), thus eliminating feedback (e.g., kickback). Also in accordance with the general teachings of the present invention, a torque limiting system is provided wherein slip is permitted when the overall torque of the system exceeds a preset and/or predetermined level.
In accordance with further teachings of the present invention, a clutch system for a power steering system is provided wherein torque transmission is permitted out in one direction only (i.e., output side), thus eliminating feedback (e.g., kickback) while also limiting overall torque to a preset and/or predetermined level. The present invention is preferably installed between the electric power steering motor and the speed reduction device on the rack of the electrically assisted power steering system, e.g., for automotive applications.
In accordance with the first embodiment of the present invention, a clutch system having a power input member and a power output member is provided, comprising:
a clutch member being coaxially disposed about the power input member, the clutch member being in physical cooperation with the power input member and the power output member, the clutch member being capable of rotating in either a first or a second direction in response to a torque force from the power input member;
an inner race member being coaxially disposed about the clutch member, the inner race member being in physical cooperation with the clutch member, the inner race member being capable of rotating in either a first or a second direction in response to a torque force from the power input member;
an outer race member being coaxially disposed about the inner race member, the outer race member being in physical cooperation with the inner race member, the outer race member being capable of rotating in either a first or a second direction in response to a torque force from the power input member; and
a roller member disposed between the inner and outer race members;
wherein the roller member is selectively operable so as to physically engage at least a portion of a surface of the outer and inner race members so as to cause the clutch member to physically engage the power output member in response to a torque force being applied to the power input member in either a first or a second direction and to physically disengage from at least a portion of a surface of the outer or inner race members so as to cause the clutch member to disengage from the power output member in response to a torque force being applied to the power output member in either a first or a second direction.
In accordance with a second embodiment of the present invention, a clutch system for use in conjunction with a power assisted steering system for a vehicle is provided, wherein the power assisted steering system includes a power steering motor, a power input member capable of rotating in either a first or a second direction in response to a torque force, and a power output member, the power input member being in physical cooperation with the power steering motor, comprising:
a clutch member being coaxially disposed about the power input member, the clutch member being in physical cooperation with the power input member and the power output member, the clutch member being capable of rotating in either a first or a second direction in response to a torque force from the power input member;
an inner race member being coaxially disposed about the clutch member, the inner race member being in physical cooperation with the clutch member, the inner race member being capable of rotating in either a first or a second direction in response to a torque force from the power input member;
an outer race member being coaxially disposed about the inner race member, the outer race member being in physical cooperation with the inner race member, the outer race member being capable of rotating in either a first or a second direction in response to a torque force from the power input member; and
a roller member disposed between the inner and outer race members;
wherein the roller member is selectively operable so as to physically engage at least a portion of a surface of the outer and inner race members so as to cause the clutch member to physically engage the power output member in response to a torque force being applied to the power input member in either a first or a second direction and to physically disengage from at least a portion of a surface of the outer or inner race members so as to cause the clutch member to disengage from the power output member in response to a torque force being applied to the power output member in either a first or a second direction.
In accordance with a third embodiment of the present invention, a power assisted steering system for a vehicle is provided, comprising:
a power steering motor;
a power output member capable of rotating in either a first or a second direction in response to a torque force, the power output member being in physical cooperation with the power steering motor; and
a clutch system disposed between the power steering motor and the power output member, the clutch system member being coaxially disposed about the power output member, the clutch system being in physical cooperation with the power output member;
wherein the clutch system is selectively operable to physically disengage from the power output member in response to a torque force being applied to the power output member in either a first or a second direction.
In accordance with a fourth embodiment of the present invention, a power assisted steering system for a vehicle is provided, comprising:
a power steering motor;
a power input member capable of rotating either in a first or a second direction in response to a torque force, the power input member being in physical cooperation with the power steering motor;
a clutch system disposed between the power steering motor and a power output member, the clutch system member being coaxially disposed about the power output member, the clutch system being in physical cooperation with the power output member, wherein the clutch system comprises:
a clutch member being coaxially disposed about the power input member, the clutch member being in physical cooperation with the power input member, the clutch member being capable of rotating in either a first or a second direction in response to a torque force from the power input member;
an inner race member being coaxially disposed about the clutch member, the inner race member being in physical cooperation with the clutch member, the inner race member being capable of rotating in either a first or a second direction in response to a torque force from the power input member;
an outer race member being coaxially disposed about the inner race member, the outer race member being in physical cooperation with the inner race member, the outer race member being capable of rotating in either a first or a second direction in response to a torque force from the power output member; and
a roller member disposed between the inner and outer race members;
wherein the roller member is selectively operable so as to physically engage at least a portion of a surface of the outer and inner race members so as to cause the clutch member to physically engage the power output member in response to a torque force being applied to the power input member in either a first or a second direction and to physically disengage from at least a portion of a surface of the outer or inner race members so as to cause the clutch member to disengage from the power output member in response to a torque force being applied to the power output member in either a first or a second direction.
In accordance with a fifth embodiment of the present invention, a torque limitation system is provided, comprising:
a housing member;
a power output member capable of rotation in response to a torque force, the power output member being capable of rotating relative to the housing member; and
at least one clutch member in physical cooperation with the housing member and the power output member, the clutch member having a compressive force applied thereto so as to establish a preset torque level between the housing member and the power output member;
wherein the at least one clutch member is selectively operable so as to slip in response to the application of a torque force in excess of the preset torque level.
In accordance with a sixth embodiment of the present invention, a torque limitation system for use in conjunction with a power assisted steering system for a vehicle is provided, comprising:
a housing member;
a power output member capable of rotation in response to a torque force, the power output member being capable of rotating relative to the housing member; and
at least one clutch member in physical cooperation with the housing member and the power output member, the clutch member having a compressive force applied thereto so as to establish a preset torque level between the housing member and the power output member;
wherein the at least one clutch member is selectively operable so as to slip in response to the application of a torque force in excess of the preset torque level.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.